Method and system for managing handover in radio access networks

ABSTRACT

A method and apparatus are provided for a handover (HO) by a Mobility Management Entity (MME). The method includes receiving, from an evolved Node B (eNB), a handover required message including information indicating whether the HO is for a circuit switched (CS) network or both a CS network and a packet switched (PS) network; splitting a voice bearer from another bearer based on the information; and transmitting a handover command message to the eNB.

PRIORITY

This application is a Continuation of U.S. Ser. No. 12/999,559, whichwas filed in the U.S. Patent and Trademark Office on Dec. 16, 2010, as aU.S. National Stage of International Application PCT/KR2009/003202,filed Jun. 16, 2009, and claims priority to Indian Patent ApplicationSerial No. 1460/CHE/2008, which was filed in the Indian Patent Office onJun. 16, 2008, and Indian Patent Application Serial No. 1460/CHE/2008,which was filed in the Indian Patent Office on Jun. 11, 2009, thecontent of each of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to managing communication inRadio Access Network (RAN), and more particularly, to managing Handover(HO) in a plurality of radio access networks.

2. Description of the Related Art

Today, several generations of radio communication systems have evolvedin the world. The several generations of the radio communication systemsincludes first generation system (1G), second generation system (2G),third generation system (3G) and fourth generation system (4G). Each ofthe generations has different transmission characteristics and differentcommunication technology.

The first generation system (1G), for example Advanced Mobile PhoneSystem (AMPS), Total Access Communications System (TACS), is based onanalog frequency modulation technology. Similarly, the second generation(2G) system, for example Global System for Mobile communications (GSM),is based on Time Division Multiple Access (TDMA). The third generation(3G) systems are based on a Wideband Code Division Multiple Access(WCDMA) air interface. Examples of a 3G system are Universal MobileTelecommunication System (UMTS) and GSM Evolution (EDGE).

The fourth generation system (4G) is an ITU specification that ispresently being developed for broadband mobile capabilities. The 4Gsystem would enable Internet Packet (IP)-based voice data and streamingmultimedia at higher speeds, compared to 3G. The radio communicationsystem is also termed as Radio Access Networks (RAN). As the number ofRANs is increasing, the geographical areas are also covered by one ormore RANs. For example, at a given geographical area there may be twoRANs that operate simultaneously, for example 2G and 3G systems.Similarly, there may be a geographical area where only one RAN isoperating, for example only 3G.

Thus with an increase in the number of RANs, for example GSM, UMTS,Wireless Local Area Network (WLAN), and EDGE, interworking betweendifferent RANs and air interface standards has become a priority. Hence,to achieve efficient interworking between different RANs and to providemore network coverage to User Equipment (UE), handover proceduresbetween RANs and communication network has become increasinglyimportant. The Handover (HO) procedure is a technical procedure forswitching an in-progress call from a coverage area of one base station(or one communication systems) to another base station (or anothercommunication system) while ensuring the continuity of the in-progresscall.

The HO in a communication system is when the UE moves from one radiocell supported by the communication system to another radio cellsupported by the communication system. For example in 2G, moving fromcoverage area of one base station associated with one service providerto another base station supported by the same or different serviceproviders. The HO between different RANs means an inter-technologyhandover, for example moving from a 3G network to a 4G network, and viseversa. The HO between different RANs is known as interlayer HO.

The different RANs have different characteristics and have differentnetwork structures that enable communication services for the UE. Hence,the HO procedures from one RAN to another RAN have to be managedefficiently. For example, voice bearers and non voice bearers that areassociated with the UE in a first RAN can be supported through PacketSwitched network and/or Circuit Switched network. Further, when the UEmoves from the first RAN to a second RAN and HO procedure is initiated,and then there may be a case that the second RAN have differentcapabilities than the first RAN. Then the voice bearers and non-voicebearers associated with the UE have to be managed efficiently based onthe capabilities of the second RAN.

Hence there exists a need to efficiently manage HO requests in RadioAccess Network (RANs).

SUMMARY OF THE INVENTION

Accordingly, the present invention is designed to address at least theproblems and/or disadvantages described above and to provide at leastthe advantages described below.

In an embodiment, a method for managing handover from a first radioaccess network to a second radio access network is provided. The methodis performed at a first network element of the first radio accessnetwork. The method includes receiving information associated with oneor more neighboring cells from a User Equipment (UE). In an embodiment,the information associated with the one or more neighboring cell ismeasurement reports. The method then decides to perform Handover (HO)based on the measurement reports for the UE from the first radio accessnetwork to the second radio access network. The first radio accessnetwork is at least a Packet Switched (PS) network and the second radioaccess network is at least a Circuit Switched (CS) network. Further, themethod identifies a target cell in the second radio access network fromthe one or more neighboring cells provided by the measurement reports.Thereafter, the method determines the target cell capabilities. Then themethod sends at least one of a handover required message and arelocation required message along with the target cell capabilities to acore network element.

In another embodiment, a method for managing Handover (HO) from a firstradio access network to a second radio access network is provided. Themethod is performed at a core network element. The method includesreceiving at least one of a handover required message and a relocationrequired message along with target cell capabilities. The method thensplits voice bearers and the non-voice bearers. Thereafter, the methodmanages HO for the voice bearers and the non-voice bearers based on thetarget cell capabilities.

In yet another embodiment, a method for managing Handover (HO) from afirst radio access network to second radio access network is provided.The method is performed at a first network element of the first radioaccess network. The method includes receiving information associatedwith one or more neighboring cells from a User Equipment (UE). In anembodiment, the information associated with the one or more neighboringcell is measurement reports. The method then decides to perform Handover(HO) based on the measurement reports for the UE from the first radioaccess network to the second radio access network. The first radioaccess network is at least a Packet Switched (PS) network and the secondradio access network is at least a Circuit Switched (CS) network.Thereafter, the method identifies a target cell in the second radioaccess network from the one or more neighboring cells provided by themeasurement reports. The method further determines the target cellcapabilities. After, determining the target cell capabilities, themethod determines a list of bearers for which HO is to be performedbased on the target cell capabilities. Thereafter, the method sends thelist of bearers to core network element for performing HO procedures forthe list of bearers.

In still another embodiment, a method for managing Handover (HO)requests from a first radio access network to a second radio accessnetwork is provided. The method is performed at a core network element.The method includes maintaining capabilities of one or more cells in adatabase. The method then receives at least one of a HO required messageand a relocation required message to perform HO for a User Equipment(UE) from the first radio access network to the second radio accessnetwork. At least one of the handover required message and therelocation required message includes information associated with atarget cell. Further, the target cell capabilities are identified fromcapabilities of one or more cells that are maintained in the database.Thereafter, the method manages HO for voice bearers and non-voicebearers based on the target cell capabilities.

In still another embodiment, a first network element of a first radioaccess network is provided. The first network element includes aprocessor and a transceiver. The transceiver in the first networkelement receives information associated with one or more neighboringcells from a User Equipment (UE). In an embodiment, the informationassociated with the one or more neighboring cell is measurement reportsassociated with one or more neighboring cells and the UE. The processorin the first network element decides to perform Handover (HO) based onthe measurement reports for the User Equipment (UE) from a first radioaccess network to a second radio access network. Further, the processoridentifies a target cell in the second radio access network from one ormore neighboring cells provided by the measurement reports. Furthermore,the processor determines the target cell capabilities. The transceiveralso sends at least one of a handover required message and a relocationrequired message along with the target cell capabilities. In anembodiment, the transceiver sends a list of bearers along with at leastone of a handover required message and a relocation required message.

In still another embodiment, a core network element is provided. Thecore network element includes a transceiver, and a processor. Thetransceiver in the core network element receives at least one of ahandover required message and a relocation required message along withtarget cell capabilities. The processor in the core network elementsplits voice bearers and non-voice bearers. Further, the processormanages Handover (HO) for the voice bearers and the non-voice bearersbased on the target cell capabilities.

In still another embodiment, a core network element is provided. Thecore network element includes a memory, a transceiver, and a processor.The memory in the core network element stores capabilities of one ormore cells in a database. The transceiver receives at least one of aHandover (HO) required message and a relocation required message alongwith information associated with a target cell to perform HO from afirst radio access network to a second radio access network. Theprocessor then identifies capabilities associated with the target cellfrom the database. Further, the processor manages HO for voice bearersand non-voice bearers based on the target cell capabilities.

The features and advantages of the present invention will become moreapparent from the ensuing detailed description of the invention taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present invention will be more apparent from thefollowing detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates an exemplary environment, where various embodimentsof the present invention can be practiced;

FIG. 2 illustrates a first network element of a first radio accessnetwork, in accordance with one embodiment of the present invention;

FIG. 3 illustrates a core network element, in accordance with oneembodiment of the present invention;

FIG. 4 illustrates a flow chart depicting a method for managing handoverfrom a first radio access network to a second radio access network, inaccordance with an embodiment of the present invention;

FIG. 5 illustrates a flow chart depicting a method for managing handoverfrom a first radio access network to a second radio access network, inaccordance with another embodiment of the present invention;

FIG. 6 illustrates a flow chart depicting a method for managing handoverfrom a first radio access network to a second radio access network, inaccordance with yet another embodiment of the present invention;

FIG. 7 illustrates a flow chart depicting a method for managing handoverfrom a first radio access network to a second radio access network, inaccordance with still another embodiment of the present invention; and

FIG. 8 illustrates a flow diagram depicting a method for managinghandover from a first radio access network to a second radio accessnetwork, in accordance with an embodiment of the present invention.

Persons skilled in the art will appreciate that elements in the figureis illustrated for simplicity and clarity and may have not been drawn toscale. For example, the dimensions of some of the elements in the figuremay be exaggerated relative to other elements to help to improveunderstanding of various embodiments of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Various embodiments of the present invention will now be described indetail with reference to the accompanying drawings. In the followingdescription, specific details such as detailed configuration andcomponents are merely provided to assist the overall understanding ofthese embodiments of the present invention. Therefore, it should beapparent to those skilled in the art that various changes andmodifications of the embodiments described herein can be made withoutdeparting from the scope and spirit of the present invention. Inaddition, descriptions of well-known functions and constructions areomitted for clarity and conciseness.

The terms used to describe various embodiments are exemplary. It shouldbe understood that these are provided to merely aid the understanding ofthe description, and that their use and definitions in no way limit thescope of the invention. Terms first, second, and the like are used todifferentiate between objects having the same terminology and are nowhere intended to represent a chronological order, as and where statedotherwise. A set is defined as a non-empty set including at least oneelement.

FIG. 1 illustrates an exemplary environment 100, where variousembodiments of the present invention can be practiced. The environment100 includes two radio access networks for example, a UTRAN and anE-UTRAN network. Though the method in the environment 100 is explainedusing a 3G network and a 4G network, it no where limits the scope of theinvention to 3G and 4G. Hence the method can be explained with the helpof any other networks. Further, the environment 100 can also includemore or less number of system elements to perform the method.

In an embodiment, the environment 100 represents a typical architecturefor Single Radio Voice Call Continuity (SR-VCC) infrastructure. In theenvironment 100, a User Equipment (UE) 102 in a first radio accessnetwork 104 (also referred as Source cell) attaches to an E-UTRAN 106using the E-UTRAN Uu interface. The E-UTRAN 106 consists of a pluralityof eNodeB entities (Not shown in figure). The plurality of eNodeBentities are connected to the Mobile Management Entity (MME) 108 usingS1-MME interface.

In an embodiment, when a user of the UE 102 initiates an IP multimediasubsystem (IMS) based voice call, then the voice call is anchored inapplication server (IMS) associated with SR-VCC continuity. In anembodiment, the data and signaling paths for the IMS based voice calluses the S1-U interface between E-UTRAN and Serving/PDN Gateway (GW)110. Further a SGi interface is used between the Serving/PDN GW and IMSnetwork entity 112.

In the environment 100, when a user of the UE 102 moves from one radioaccess network (for example a Source cell 104) to another radio accessnetwork (for example a Target cell 120) during an in-progress call aHandover (HO) is required. In an embodiment, when the UE 102 moves fromthe E-UTRAN network 104 to the GERAN/UTRAN network 120 during thein-progress voice call, then HO is required from the E-UTRAN network 104to the UTRAN/GERAN network 120. The E-UTRAN supports only PS (PacketSwitched) network and the GERAN/UTRAN supports PS and CS (CircuitSwitched) network. Hence, the UE 102 moves from a PS network to anetwork that supports PS and CS network.

Therefore eNodeB in the E-UTRAN 106 detects that a Single radio voicecall continuity Handover (HO) is required to be performed towards targetGERAN/UTRAN network 120. Then, eNodeB sends a handover required messageto MME 108 over S1-MME interface. In an embodiment, the MME 108 alsoreceives target cell capabilities. For example, the MME 108 receives thecapabilities associated with the target cell 120. For example, thecapabilities of the target cell include capabilities of the URAN/GERANnetwork. For example, the target cell, in the environment 100, is aPacket Switched (PS) network and a Circuit Switched (CS) network.

The MME 108 then identifies the voice bearers and the non-voice bearersassociated with the UE 102 while the HO procedure is in progress. TheMME 108 then starts the handover of the voice bearers towards a CSdomain of the target cell 120 by sending message over Sv interface to aMobile Switching Center (MSC) Server 116. The MSC server 116 thentriggers a session transfer of the IMS layer by sending session transferrequest to the IMS application server.

The MME 108 then manages the non-voice bearers. In an embodiment, theMME 108 starts a PS-PS handover for the non-voice bearers when thetarget cell 120 supports both CS and PS network and also Dual TransferMode (DTM) handover. In another embodiment, the MME 108 suspendsnon-voice bearers when the target cell in the second radio accessnetwork support CS and PS network but does not support DTM. In yetanother embodiment, the MME 108 deactivates the non-voice bearers whenthe target cell does not support PS network.

In an embodiment, for PS-PS handover of non-voice bearers the MME 108sends a message to SGSN 114 over S3 interface. Once session transfer isinitiated and the handover preparation is complete in the target cell120, the MME 108 sends a HO command to the UE 102 via eNodeB. The UE 102on receiving the HO command moves to target cell resources. Then thetarget cell 120 detects presence of the UE 102. In an embodiment, theUTRAN/GERAN 118 informs the target MSC server 116 via Iu-cs/A interfaceand the target SGSN 114 via Iu-ps/Gb interface about the HO. Further,the MSC server 116 and the SGSN 114 inform the MME 108 of handovercompletion via Sv and S3 interfaces respectively. Thereafter, the MME108 releases resources reserved for the UE 102 on the source cell 104.

FIG. 2 illustrates a first network element of the first radio accessnetwork 200, in accordance with one embodiment of the present invention.To explain the first network element, references will be made to FIG. 1.However, it will be apparent to a person ordinarily skilled in the artthat the present embodiment can be explained with the help of any othersuitable embodiment of the present invention.

In an embodiment, the first network element is a node that enablescommunication devices, associated with fourth generation communicationnetwork, to communicate with other communication devices associated withany communication networks. In an embodiment, the first network elementis an eNodeB that is used for establishing communication in E-UTRANnetwork.

In the environment 100, the first network element is associated with theUser Equipment (UE), for example UE 102 which is associated with theE-UTRAN network 104. The first network element includes a transceiver202 and a processor 204.

The transceiver 202 in the first network element receives, informationassociated with one or more neighboring cells from the UE. In anembodiment, the transceiver 202 also receives measurement reportsassociated with the one or more neighboring cells from the UE 102. In anembodiment, the measurement reports include signal strength and/orresources availability associated with the one or more neighboringcells.

The processor 204 in the first network element decides to performHandover (HO) based on the measurement reports for the UE from a firstradio access network to a second radio access network. For example, theprocessor 204 decides to perform Handover (HO) based on the measurementreports for the UE 102 from the first radio access network 104 to thesecond radio access network 120. The processor 204 then identifies atarget cell from the one or more neighboring cells provided by themeasurement reports.

In an embodiment, the one or more neighboring cells are one or morecells that are available to perform Handover procedures by the UE 102.Hence, the one or more neighboring cells are one or more cells that areavailable around the UE 102 when the UE 102 is moving out of a coveragearea of the first radio access network 104. In an embodiment, the targetcell is a cell that selected to perform HO procedures for the UE.

Further, the processor 204 determines the target cell capabilities. Inan embodiment, the processor identifies a list of bearers for which HOis possible and a list of bearers for which HO is not possible based onthe target cell capabilities. In an embodiment, the target cellcapabilities are the network support capabilities of the target cell.For example, the target cell capabilities include information regardingwhether the target cell supports only Circuit Switched (CS) network,both CS and Packet Switched (PS) UTRAN network, both CS and PS GERANnetwork with DTM support and DTM Handover support, both CS and PS GERANnetwork without DTM support but with PS Handover support or both CS andPS GERAN network without DTM and without PS handover support.

Thereafter, the transceiver 202 sends at least one of a handoverrequired message and a relocation required message along with the targetcell capabilities. In an embodiment, the transceiver sends the list ofbearers for which the HO is possible. In an embodiment, the handoverrequired message along with target cell capabilities is sent to a corenetwork element. In another embodiment, the relocation required messagealong with the target cell capabilities is sent to the core network.

FIG. 3 illustrates a core network element, in accordance with oneembodiment of the present invention. To explain the core networkelement, references will be made to FIG. 1. However, it will be apparentto a person ordinarily skilled in the art that the present embodimentcan be explained with the help of any other suitable embodiment of thepresent invention. In an embodiment, the core network element enablesUser Equipment (UE) to perform Handover (HO) procedures. In anembodiment, the core network element is a Mobile Management Entity(MME). In another embodiment, the core network element is a ServingGeneral Packet Radio Service (GPRS) Support Node (SGSN). For example, inthe environment 100, the core network element is MME 108 or SGSN 114.

The core network element includes a transceiver 302 and a processor 304.The transceiver 302 in the core network element receives at least one ofa handover required message and a relocation required message along withtarget cell capabilities. In an embodiment, the handover requiredmessage along with the target cell capabilities is received from thefirst network element. In another embodiment, the relocation requiredmessage along with the target cell capabilities is received from thefirst network element. In the environment 100, the handover requiredmessage along with the target cell capabilities is received from theeNodeB associated with the E-UTRAN 106.

The processor 304 in the core network element splits voice bearers andnon-voice bearers. In an embodiment, the non-voice bearers and the voicebearers are segregated from a list of bearers received from the firstnetwork element. Further, the processor 304 manages Handover (HO) forthe voice bearers and the non-voice bearers based on the target cellcapabilities.

In an embodiment, the core network element also includes a memory 306.The memory 306 in the core network element stores capabilities of one ormore cells in a database. In an embodiment, the memory 306 is configuredin the core network element. In another embodiment, the memory 306 isexternally associated with the core network element. In an embodiment,the memory 306 is a volatile memory. In another embodiment, the memory306 is a non-volatile memory. In the environment 100, the database inthe memory 306 is associated in the Home Subscriber Server (HSS) 122.

In an embodiment, the transceiver 302 receives at least one of ahandover required message and a relocation required message along withinformation associated with the target cell to perform HO from a firstradio access network to a second radio access network. The processor 304then identifies capabilities associated with the target cell from thedatabase. For example, the processor 304 after receiving target cellinformation matches the target cell with the one or more cellsregistered in the memory 306. Thereafter, the processor 304 identifiesthe target cell capabilities from the capabilities stored in the memory306. Further, the processor 304 manages HO for the voice bearers and thenon-voice bearers based on the target cell capabilities stored in thememory 306.

FIG. 4 illustrates a flow chart depicting a method for managing handoverfrom a first radio access network to a second radio access network, inaccordance with an embodiment of the present invention. In anembodiment, the method is performed by a first network element of thefirst radio access network. To explain the method 400, references willbe made to FIG. 1. However, it will be apparent to a person ordinarilyskilled in the art that the present embodiment can be explained with thehelp of any other suitable embodiment of the present invention. Themethod 400 can also include more or fewer number of steps as depicted inFIG. 4. Further, the order of the steps may also vary.

At step 402 the method 400 is initiated. In an embodiment, the method isinitiated at first network element. In an embodiment, the first networkelement of the first radio access network is an eNodeB, a NodeB or aRadio Network Controller (RNC). An example of the first network elementincludes, but is not limited to, eNodeB, for example eNodeB in theE-UTRAN 106. At step 404, information associated with one or moreneighboring cells is received from a User Equipment (UE). Theinformation associated with the one or more neighboring cell ismeasurement reports. In an embodiment, the measurement reports includesignal strength and resources availability associated with the one ormore neighboring cells.

At step 406, the method decides to perform Handover (HO) based on themeasurement reports for the UE from the first radio access network tothe second radio access network. For example, the method decides toperform Handover (HO) based on the measurement reports for the UE 102from the first radio access network 104 to the second radio accessnetwork 120.

In an embodiment, the first radio access network is a Packet Switched(PS) network. In an embodiment, the second radio access network is aCircuit Switched (CS) network. In another embodiment, the second radioaccess network is the CS network and the PS network that supports DualTransfer Mode (DTM). In another embodiment the second radio accessnetwork is a UTRAN network which support both CS and PS simultaneously.In yet another embodiment, the second radio access network is the CSnetwork and PS network that does not supports Dual Transfer Mode (DTM).

In an embodiment, the first radio access network is fourth generationmobile radio communication system. In the embodiment, the first radioaccess network is an Enhanced Universal Terrestrial Radio Access Network(E-UTRAN) or a UTRAN. In an embodiment, the second radio access networkis a third generation mobile radio communication system or a secondgeneration mobile radio communication system. In the embodiment, thesecond radio access network is a UTRAN or a General Packet Radio AccessService (GPRS) Enhanced Data for GSM Evolution (EDGE) Radio AccessNetwork (RAN) (GERAN).

At step 408, the method identifies a target cell in the second radioaccess network from the one or more neighboring cells provided by themeasurement reports. The target cell is a cell to which the HO procedureis initiated.

At step 410, the method determines the target cell capabilities. In anembodiment, the target cell capabilities are network supportcapabilities of the target cell. For example, in the environment 100 thetarget cell capabilities are the capabilities of the target cell 120.Thereafter, at step 412, the method sends at least one of a handoverrequired message and a relocation required message along with the targetcell capabilities to a core network element.

In an embodiment, the core network element is a Mobile management Entity(MME). In another embodiment, the core network element is a ServingGeneral Packet Radio Service (GPRS) Support Node (SGSN). In anembodiment, the method also indicates the core network element about aSingle Radio Voice Call Continuity handover (SRVCC) operation. The SRVCCis a procedure that is defined in TS 23.216 standards. The SR-VCCoperations are used for voice call continuity between Internet Protocol(IP) Multimedia Subsystem (IMS) over PS access network and CS accessnetwork for calls that are anchored in IMS. The SRVCC is used when theUE is capable of transmitting/receiving on only one of the accessnetworks at a given time.

In an embodiment, the method 400 further enables core network element tomanage voice bearers and non-voice bearers. In an embodiment, the corenetwork element splits the voice bearers and non-voice bearers based ontarget cell capabilities, a Quality of Service Class Identifier (QCI)associated with the voice bearers and/or SRVCC handover indication. Inan embodiment, the QCI notifies the core network element that the bearerbelongs to the voice call.

In an embodiment, the method continues HO of the voice bearer from firstradio access network to second radio access network based on the targetcell capabilities. In an embodiment, the first radio access network is aPS network and the second radio access network is at least a CS network.Hence, in the embodiment, the HO of the voice bearer is initiated fromPS network to CS network. Further, the method suspends or deactivatesthe non-voice bearers based on the target cell capabilities.

For example, when the target cell supports CS network and does notsupport PS network and Dual Transfer Mode (DTM), then the methoddeactivates the non-voice bearers. Similarly, when the target cellsupports CS network and the PS network but does not support DTM then themethod suspends the non-voice bearers. Hence, the suspended non-voicebearer can be resumed when the HO for the voice bearer is completed andUser Equipment moves to the target side.

In an embodiment, the HO of the voice bearer and the non-voice bearersis continued from the first radio access network to the second radioaccess network based on the target cell capabilities. In an embodiment,the first radio access network is a PS network and the second radioaccess network is a CS network and a PS network.

Hence, in the embodiment, the method initiates Packet Switched (PS) toCircuit Switched (CS) HO for the voice bearers and PS to PS HO for thenon-voice bearers. Therefore, the voice bearers that is associated withthe PS network in the first radio access network will be associated withthe with CS network in the second radio network. Further, the non-voicebearer that is associated with the PS network in the first radio accessnetwork is associated with the PS network in the second radio accessnetwork. At step 414 the method is terminated.

FIG. 5 illustrates a flow chart depicting a method for managing handoverfrom a first radio access network to a second radio access network, inaccordance with another embodiment of the present invention. To explainthe method 500, references will be made to FIG. 1. However, it will beapparent to a person ordinarily skilled in the art that the presentembodiment can be explained with the help of any other suitableembodiment of the present invention. The method 500 can also includemore or fewer number of steps as depicted in FIG. 5. Further, the orderof the steps may also vary. In an embodiment, the method is performed bya core network element.

At step 502 the method is initiated. At step 504, the method receives atleast one of a handover required message and a relocation requiredmessage along with target cell capabilities. In an embodiment, themethod is performed at a core network element. Examples of core networkelement include, but are not limited to, Mobile Management Entity (MME)and a Serving General Packet Radio Service (GPRS) Support Node (SGSN).

In an embodiment, the handover required message or relocation requiredmessage along with target cell capabilities is received from the firstnetwork element, for example eNodeB in E-UTRAN network 104. At step 506,the method splits voice bearers and the non-voice bearers. In anembodiment, the voice bearers and the non-voice bearers are separatedbased on a Quality of Service Class Identifier (QCI) associated with thevoice bearers and SRVCC handover indication.

In an embodiment, the voice and non voice bearers are extracted from alist of all active bearers (voice and non-voice) associated with theUser Equipment along with the target cell capabilities. For example, thecore network element, for example the MME 108, receives the list of allthe active bearers along with the target cell 120 capabilities from theeNodeB in E-UTRAN 106.

Thereafter, at step 508, the method manages HO for the voice bearers andthe non-voice bearers based on the target cell capabilities. In anembodiment, the method continues HO of the voice bearer from the firstradio access network to the second radio access network and suspends ordeactivates the non-voice bearers based on the target cell capabilities.In another embodiment, the method continues HO of the voice bearers andthe non-voice bearers from the first radio access network to the secondradio access network based on the target cell capabilities. At step 510the method is terminated.

FIG. 6 illustrates a flow chart depicting a method for managing handoverfrom a first radio access network to a second radio access network, inaccordance with yet another embodiment of the present invention. Toexplain the method 600, references will be made to FIG. 1. However, itwill be apparent to a person ordinarily skilled in the art that thepresent embodiment can be explained with the help of any other suitableembodiment of the present invention. The method 600 can also includemore or fewer number of steps as depicted in FIG. 6. Further, the orderof the steps may also vary. In an embodiment, the method is performed ata first network element. In an embodiment, the method is performed by afirst network element of the first radio access network. In anembodiment, the method is performed by eNodeB in the E-UTRAN 106.

At step 602 the method is initiated. At step 604, information associatedwith one or more neighboring cells is received from a User Equipment(UE). The information associated with the one or more neighboring cellis measurement reports. In an embodiment, the measurement reportsinclude signal strength and resources availability associated with theone or more neighboring cells.

At step 606, the method decides to perform Handover (HO) based on themeasurement reports for the User Equipment (UE), for example the UE 102,from the first radio access network to the second radio access network.In an embodiment, the first radio access network is a Packet Switched(PS) network and the second radio access network is at least a CircuitSwitched (CS) network.

For example, the first radio access network is an Enhanced UniversalTerrestrial Radio Access Network (E-UTRAN) or a UTRAN and the secondradio access network is a UTRAN or a General Packet Radio Access Service(GPRS) Enhanced Data for GSM Evolution (EDGE) Radio Access Network (RAN)(GERAN).

At step 608, the method identifies a target cell in the second radioaccess network from the one or more neighboring cells provided by themeasurement reports. The target cell is a cell to which the HO procedureis intimated. At step 610, the method determines the target cellcapabilities. In an embodiment, the target cell capabilities are thenetwork support capabilities of the target cell.

At step 612, a list of bearers for which HO is to be performed isdetermined based on the target cell capabilities. At step 614, the listof bearers is sent to a core network element for performing HOprocedures for the list of bearers. For example, the list of bearers issent by the eNodeB to a Mobile management Entity (MME) or a ServingGeneral Packet Radio Service (GPRS) Support Node (SGSN), for example theMME 108 or the SGSN 114.

In an embodiment, the list of bearers includes only a list of voicebearers based on the target cell capabilities. In the embodiment, themethod suspends or deactivates the non-voice bearers based on the targetcell capabilities. In an embodiment, the list of bearers includes acombined list of voice bearers and non-voice bearers based on the targetcell capabilities.

For example, when the target cell supports CS network and does notsupport PS network and Dual Transfer Mode (DTM), then the methoddeactivates the non-voice bearers and sends only a list of voicebearers. Similarly, when the target cell supports CS network and the PSnetwork but does not support DTM then the method suspends the non-voicebearers and sends a list of voice bearers and suspends the non-voicebearers for a predetermined interval of time. Hence, the suspendednon-voice bearers can be resumed when the HO for the voice bearer iscompleted. In another example, when the target cell is a CS network anda PS network and also supports DTM then a list of voice bearer andnon-voice bearers is sent to the core network element. At step 616, themethod is terminated.

FIG. 7 illustrates a flow chart depicting a method for managing handoverfrom a first radio access network to a second radio access network, inaccordance with still another embodiment of the present invention. Toexplain the method 700, references will be made to FIG. 1. However, itwill be apparent to a person ordinarily skilled in the art that thepresent embodiment can be explained with the help of any other suitableembodiment of the present invention. The method 700 can also includemore or fewer number of steps as depicted in FIG. 7. Further, the orderof the steps may also vary. In an embodiment, the method is performed ata core network element.

At step 702 the method 700 is initiated. At step 704, the method 700maintains capabilities of one or more cells in a database. In anembodiment, capabilities of the one or more cells are stored in thememory. In an embodiment, the memory is configured in the core networkelement. In another embodiment, the memory is externally associated withthe core network element. In the environment 100, the database in thememory is associated in the Home Subscriber Server (HSS) 122.

At step 706, the method receives at least one of a handover requiredmessage and a relocation required message along with informationassociated with a target cell to perform HO from the first radio accessnetwork to the second radio access network. At step 708, the target cellcapabilities are identified from the capabilities of the one or morecells stored in the database. For example, after receiving target cellinformation, the method matches the target cell with the one or morecells registered in the database. Further, the method identifies thecapabilities maintained in the database associated with a cell that ismatched with the target cell.

Thereafter, at step 710, the method manages HO for the voice bearers andthe non-voice bearers based on the target cell capabilities stored inthe database. At step 712, the method 700 is terminated.

FIG. 8 illustrates a flow diagram depicting a method for managinghandover from a first radio access network to a second radio accessnetwork, in accordance with an embodiment of the present invention. Toexplain the method 800, references will be made to FIG. 1. However, itwill be apparent to a person ordinarily skilled in the art that thepresent embodiment can be explained with the help of any other suitableembodiment of the present invention.

In the environment 100, the UE 102 periodically determines measurementreports of one or more neighboring cells. At step 802, the UE 102 sendsthe measurement reports to the Source E-UTRAN 106. At step 804, themethod at E-UTRAN 106 decides for a HO. Then the source E-UTRAN 106identifies a target cell in the second radio access network 120 to whichthe HO is performed provided by the measurement reports received from UE102. The E-UTRAN also identifies the target cell capabilities. At step806 at least one of a handover required message and a relocationrequired message along with the target cell capabilities is sent to theSource MME 108.

At step 808, the MME 108 manages voice bearers and the non-voicebearers. In an embodiment, the core network element splits the voicebearers and the non-voice bearers based on target cell capabilities, aQuality of Service Class Identifier (QCI) associated with the voicebearers and/or SRVCC handover indication. In an embodiment, the methodcontinues HO of the voice bearer from source radio access networkE-UTRAN 106 to a second radio access network 810 based on the targetcell capabilities. In an embodiment, the source radio access network isa PS network and the target radio access network is only a CS network.Hence, in the embodiment, the HO of the voice bearer is initiated fromPacket Switched (PS) network to Circuit Switched (CS) network.

In another embodiment, the non-voice bearers are suspended ordeactivated based on the target cell capabilities. For example, when thetarget cell supports CS network and does not support PS network and DualTransfer Mode (DTM), then the method deactivates the non-voice bearers.Similarly, when the target cell supports CS network and the PS networkbut does not support DTM then the method suspends the non-voice bearers.Hence, the suspended non-voice bearers can be resumed when the HO forthe voice bearer is completed and User equipment moves to target side.

In an embodiment, the HO of the voice bearer and the non-voice bearersis continued from the source radio access network 104 to the secondradio access network 810 based on the target cell capabilities. In anembodiment, the first radio access network is a PS network and thesecond radio access network is a CS network and a PS network. Hence, inthe embodiment, the method initiates Packet Switched (PS) to CircuitSwitched (CS) HO for the voice bearers and Packet Switched (PS) toPacket Switched (PS) HO for the non-voice bearers.

At step 812, the HO preparation and resource reservation is performed.Further session transfer preparation involving IMS is also performed. Atstep 814, the MME 108 sends the HO command to the UE 102. For example,when session transfer is initiated and the handover preparation iscomplete in the target cell, the MME 108 sends a HO command to the UE102. At step 816, the method tunes the target cell after receiving themessage from MME. Hence, the UE 102 on receiving the HO command moves totarget cell side. At step 818 the target side detects presence of the UE102. Further, at step 820 the target side informs the MME 108 ofhandover completion. Thereafter, the MME 108 releases resources reservedfor the UE 102 on the source cell 104.

Various embodiments of the present invention described above provide thefollowing advantages. The present invention provides a method formanaging Handover (HO) in plurality of radio access networks. Thepresent invention enables a user to move from one radio access networkto another radio access network during an in-progress call withoutinterruption. Further, the method has no impact on the existing radioaccess network and thus it can be implemented without changing theexisting radio access network systems.

The method also minimizes the handover preparation phase. In addition,HO from a higher generation communication network, for example thefourth generation radio access network to the lower generation radioaccess network, for example third generation radio access network iscarried out easily without any impact on a Quality of Service.

Further, the method provides efficient compatibility during HO from aradio access network supporting only Packet Switched (PS) network toanother radio access network supporting Circuit Switched (CS) and/or PS.Further, during the HO process, the method effectively manages voicebearers and non-voice bearers. The method in-advance identifies a listof bearers that can be managed by the target cell. Hence, the overalloverhead of HO process is reduced effectively and this increasesefficiency of the radio access networks.

The method avoids unnecessary signaling as a core network element (forexample MME or SGSN) is updated with sufficient information about thetarget cell capabilities. Hence the core network element can takecorrect decision associated with handling of non-voice bearers.

While certain embodiments of the present invention have been illustratedand described, it will be clear that the present invention and itsadvantages are not limited to these embodiments only. Numerousmodifications, changes, variations, substitutions and equivalents willbe apparent to those skilled in the art without departing from thespirit and scope of the present invention as described in the claims.

What is claimed is:
 1. A method for a handover (HO) by a MobilityManagement Entity (MME), the method comprising: receiving, from anevolved Node B (eNB), a handover required message including firstinformation indicating whether the HO is for a circuit switched (CS)network or both a CS network and a packet switched (PS) network;splitting a voice bearer from a non-voice bearer based on the firstinformation; initiating a PS to CS HO for the voice bearer suspending aHO for the non-voice bearer, if a second radio access network does notsupport a dual transfer mode (DTM); and transmitting a handover commandmessage to the eNB, wherein the suspended non-voice bearer is resumed,if a call corresponding to the voice bearer is terminated and if the UEis in the second radio access network, wherein second informationassociated with the resuming of the suspended non-voice bearer istransmitted to a core network entity, and wherein the voice bearer andthe non-voice bearer are associated with the PS network in a first radioaccess network and the voice bearer is associated with the CS network inthe second radio access network and the non-voice bearer is associatedwith the PS network in the second radio access network.
 2. The method ofclaim 1, further comprising: performing the HO of the voice bearer fromthe PS network to the CS network.
 3. An apparatus for a handover (HO)comprising: a transceiver; and a processor for controlling to receive,via the transceiver, from an evolved Node B (eNB), a handover requiredmessage including first information indicating whether the HO is for acircuit switched (CS) network or both a CS network and a packet switched(PS) network, to split a voice bearer from a non-voice bearer, based onthe first information, to initiate a PS to CS HO for the voice bearer,to suspend a HO for the non-voice bearer, if a second radio accessnetwork does not support a dual transfer mode (DTM), and to transmit ahandover command message to the eNB, wherein the suspended non-voicebearer is resumed, if a call corresponding to the voice bearer isterminated and if the UE is in the second radio access network, whereinsecond information associated with the resuming of the suspendednon-voice bearer is transmitted to a core network entity, and whereinthe voice bearer and the non-voice bearer are associated with the PSnetwork in a first radio access network and the voice bearer isassociated with the CS network in the second radio access network andthe non-voice bearer is associated with the PS network in the secondradio access network.
 4. The apparatus of claim 3, wherein the processorcontrols to perform the HO of the voice bearer from the PS network tothe CS network.
 5. The apparatus of claim 3, wherein the apparatuscomprises at least one of a mobile management entity (MME) and a servinggeneral packet radio service (GPRS) support node (SGSN).